It is common practice to provide a tractor with a drawbar which connects an implement in draft relation to the tractor. Over the years, a trend has developed toward large folding type implements. Front folding implement configurations appear to be a particularly popular design.
Front folding implements typically include a main or center section with a horizontally elongated central yoke or tongue which connects the implement to the drawbar of the tractor. Left and right wing sections are pivotally connected to the center section. The wing sections are spread to the side of the center section when the implement is used in the field. The wing sections fold forwardly and the free ends of the wing sections are supported by the tongue to facilitate transportation of the implement.
Each section of the implement includes a wheeled frame which can have different configurations. An implement frame typically includes rearwardly extending frame members and a series of horizontally elongated tool bars rigidly connected to and extending laterally between the frame members. Depending upon the particular implement design, a plurality of laterally spaced row units or ground engaging elements or tools are mounted to each tool bar.
Vertically displacable wheel assemblies arranged forwardly of the tool bars regulate the elevation of the implement frame relative to the ground. Arranging the wheel assemblies forward of the tool bars is becoming a much more common practice. This is due to the need and desire to laterally adjust the row units or ground engaging elements along the length of each tool bar so as to provide the farmer with versatility regarding adjusting row spacings on seeding and cultivating implements.
While facilitating farming techniques, the increased size of today's implement has created problems in that relatively large vertical loads are applied to the tractor drawbar. It is not uncommon for such loads to exceed manufacturer's requirements for the tractor drawbar.
One approach at solving the drawbar loading problem involves using support chains which depend from the tractor and are tensioned in response to a downward or positive load being applied to the drawbar. Alternatively, specially designed drawbars have been fitted to the lift links of a conventional three-point tractor hitch mechanism. As will be appreciated, specially designed drawbars require several extra components and, thus, add considerable expense to the manufacturer and to the former.
It is important to note that these heretofore known devices offer support only in a downward or positive loading mode. Implements having the wheel assemblies arranged forwardly of the tool bars, however, are capable of imparting both a negative or upwardly directed load and the positive downwardly directed load to the drawbar depending upon the mode of implement operation. Although the tension bearing ability of the support chains allows them to offer drawbar support against positive or downward loads, these support chains neither can nor do offer support against negative or upwardly directed drawbar loads. Similarly, heretofore known specially designed drawbars do not offer support against negative or upward loads applied against the drawbars. This is because the hydraulic motors used to position the lift links which carry the specially designed drawbar are typically designed to offer little or no resistance to upward movement of the lift links. Accordingly, none of the heretofore known devices are capable of offering drawbar support to counter both positive and negative loads imparted to the tractor drawbar.
Thus, there is a need and a desire for an economical drawbar hitch assembly which couples a farm implement in draft relation to the tractor and which provides drawbar support to counter both positive and negative loads.